Yes, the $9999 price was solely to get you in the door and it worked, didn't it? It's called a lost leader and they tagged the dollar price, not you! Hoping to make a profit with added accessories and addons. However, the $15,200 final price was an real insult and you should be really ticked. MSRP price has nothing to do with it as NOBODY in their right mind would ever pay MSRP.
$2900 added on for mostly BS is totally wrong and good for you for not allowing it. Yes there are some shipping costs and reasonable prep costs but a $300 document fee is a pure joke. Bet you wouldn't have even gotten a tiny kiss with that ________.
$13,500 OTD makes a lot more sense with everything as you stated but I'd sure tell them in no kind words but diplomatically that they had not given you a warm and fuzzy feeling with their games and that buying from them again will be predicated on watching what kind of service etc you get on the trailer if needed. Also give them the clear verbal hint that "word of mouth" is very powerful and you want to have a good relationship with them, so their dealing's reaction going forward is in their court! So let's make it a 2 way happy relationship now!